feat: Change colors for links to red

[trashutz]

I changed some colors to red.

I used:

• 991916 -> Main color from logo

• ce8380 -> for hover

• a24443 -> for dark mode because #991916 was a bit too dark

Two CSS variables are still blue (but I think are not in use at the moment):

• $pagination-link-color
• $blockquote-color